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From: Jeff King <peff@peff.net>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Ævar Arnfjörð Bjarmason <avarab@gmail.com>,
	Martin Langhoff <martin.langhoff@gmail.com>,
	Git Mailing List <git@vger.kernel.org>
Subject: Re: Git ransom campaign incident report - May 2019
Date: Fri, 17 May 2019 18:20:31 -0400
Message-ID: <20190517222031.GA17966@sigill.intra.peff.net> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.1905172121130.46@tvgsbejvaqbjf.bet>

On Fri, May 17, 2019 at 09:39:55PM +0200, Johannes Schindelin wrote:

> > Of course I suspect there are many cases where people _do_ need to store
> > the password in plaintext, because an automated system needs to fetch
> > with it. They can use the plaintext git-credential-store, but it's
> > slightly more hassle. And it doesn't really _solve_ the problem (though
> > perhaps it would be harder to accidentally expose it with your web
> > server!).
> 
> One thing that we actually *could* do here is to anonymize the URLs stored
> under remote.origin.url when cloning. In no other circumstance that I can
> think of do we take an URL from some command-line parameter that is not
> *explicitly* intended for storing in the config.

Good point. That's a plausible way that these end up in config even when
they're not needed and it wasn't intended by the user.

> Combined with that warning "You cloned via a URL that contains
> credentials; for security reasons, the credentials were scrubbed before
> storing this in your Git config. Please consider using a credential
> manager instead of storing secrets in your Git config." this should
> provide a reasonable compromise.

Yeah, we'd definitely want to warn the user. Some people might find it
irritating because a follow-up fetch would require an interactive
password. We might need to make sure the escape hatch is pretty turnkey.
The simplest thing is just a "--save-password" option to override this,
but it would be nice if there's an out-of-the-box solution with a
credential helper.

We can use credential-store as a general solution. That's still
sticking the password in the filesystem in plaintext, but the file is
0700 by default, and it's not in the repo directory).

Unfortunately converting:

  git clone https://user@pass:example.com/repo.git

into a safer use of credential-store is a little tricky, because seeding
the store is generally only done interactively. What if we did this:

  1. Do not ever write the password part of a URL into config.

  2. When we extract the user/pass out of a URL, put them into the
     credential struct, so that when we successfully authenticate, we
     trigger storage. This _might_ actually happen already, but we
     should definitely confirm it.

  3. If the user has no credential helper defined, then do one of:

     a. Warn them that the credential was not recorded, but that they
        can use "git clone -c credential.helper=store" as a fallback
	(but probably worded in a way to recommend using something
	stronger if possible).

	This is slightly annoying because following the advice requires
	re-cloning. Fixing it up from there is more like:

	  git config credential.helper store
	  git fetch
	  [interactively input password]

     b. Just use credential-store. Optionally notify them of what
         happened (and that they might want to choose a better helper).

I hate the magical-ness of 3b, because credential-store really _isn't_
the best choice. It's just better than the current behavior. At the same
time, by doing it automatically, the existing flow they were using just
works, and is moderately better.

> Judging from looking at my own automated jobs, it does not appear that you
> would *ever* need to store such credentials in the Git config, anyway. If
> you need to, say, push to a repository, you can always store the full URL
> (or the credentials) in a secret variable.

Yes, that's definitely the way you _should_ do it. I think the problem
is that handling secret storage is tricky and system-specific, and the
people who are affected here are ones who just didn't think about it. If
we can make even a moderate improvement without the user having to do
anything differently, it's worth considering.

-Peff

  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-15 17:49 Martin Langhoff
2019-05-15 18:59 ` Ævar Arnfjörð Bjarmason
2019-05-16  4:27   ` Jeff King
2019-05-17 19:39     ` Johannes Schindelin
2019-05-17 22:20       ` Jeff King [this message]
2019-05-17 23:13         ` Martin Langhoff
2019-05-19  5:07         ` Jeff King
2019-05-19  5:10           ` [PATCH 1/3] transport_anonymize_url(): support retaining username Jeff King
2019-05-19 23:28             ` Eric Sunshine
2019-05-20 16:14             ` René Scharfe
2019-05-20 16:36             ` Johannes Schindelin
2019-05-20 16:43             ` Johannes Schindelin
2019-05-19  5:12           ` [PATCH 2/3] clone: avoid storing URL passwords in config Jeff King
2019-05-19  5:16           ` [PATCH 3/3] clone: auto-enable git-credential-store when necessary Jeff King
2019-05-20 11:28             ` Eric Sunshine
2019-05-20 12:31               ` Jeff King
2019-05-20 16:48                 ` Johannes Schindelin
2019-05-20 13:56             ` Ævar Arnfjörð Bjarmason
2019-05-20 14:08               ` Jeff King
2019-05-20 15:17                 ` Ævar Arnfjörð Bjarmason
2019-05-20 15:24                   ` Jeff King
2019-05-20 17:08             ` Ævar Arnfjörð Bjarmason
2019-05-20 14:43           ` Git ransom campaign incident report - May 2019 Johannes Schindelin

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